Field of the Invention
The invention pertains to motor vehicles, and particularly to a method of controlling the drive train of a motor vehicle and to an integrated drive train control system.
Prior art control systems for the engine, transmission and secondary assemblies of a motor vehicle operate largely independently; that is, they establish the operating point and operating mode of the controlled assembly largely independently of one another. Means are also available for communication among the various components of the drive train of a motor vehicle, for instance in the form of a CAN bus or the like, but these means are predominantly used only for exchanging sensor data in the course of multiple utilization. Moreover, the control systems affect one another by means of communication in certain operations, for instance to make for smoother shifting by reducing the engine torque upon a change of transmission ratio in the transmission.
Other examples include engine drag torque control during braking, and braking intervention or torque reduction in traction control if drive slip arises. A system for linking together systems in the automobile has become known heretofore that seeks an integrated drive train control system for a motor vehicle by means of which the position of the accelerator pedal is interpreted as a wheel torque or transmission output torque desired by the driver and used for calculating desired values for the engine and transmission of the motor vehicle (F & M 101 (1993) 3, pp. 87-90). The goal of the overriding optimization proposed in that publication, of the parts of the system embodied by the engine control unit, electronic accelerator pedal and transmission control unit, is to reduce fuel consumption and to improve the drivability, in particular with regard to the spontaneous reaction to movements of the accelerator pedal.
The drive train (engine, transmission, differential, drive wheels) can be optimized by taking into account the following various criteria dynamically during one drive cycle: drive mode (for example, sporty or economy). In general, the driver always remains the chief decision maker for these optimization criteria, even in metropolitan areas with heavy traffic, traffic jams, and variable ozone concentrations. Moreover, increasing numbers of driver support systems are becoming established in vehicles, such as vehicle navigation systems with multimedia characteristics (radio, telephone, etc.) and the capability of receiving information during a trip.